Hi !> I got one parser named 'ELSA'. It has the option to write the AST into> an XML file. I think i can use some xml parser to get an AST data> structure from that. But is there any other tool that provides an AST> that can be directly used in my program?

Look at ANTLR tool (http://www.antlr.org/). It produces AST and you can
parse this one in your program.
--
dima